Cell construction



April 24, 1934. E, J, MCEAQHRON E1- AL 1,956,243

CELL CONSTRUCTION Filed NOV. 7, 1931 Patented Apr. 24, 1934 UNITEDSTATES PATENT OFFICE CELL CONSTRUCTION a corporation of WisconsinApplication November 7, 1931, Serial No. 573,550

5 Claims.

This invention relates to a new and improved construction forgalvanicncells commonly used in assembling dry batteries, and moreparticularly to the type of cells known in the art as 5 dry Acells ofthe bag type. By the expression bag type is meant that type of cellhaving a central core composed of a carbon pencil and a mixture ofdepolarizing material, this core not being compressed directly into-alined zinc can l as in the case of paper-lined cells, but beingfabricated as a separate unit and afterwards.

put into operative relationship with the zinc can,

by means of an annular layer of gelatinous electrolyte positionedbetween the core and the l zinc can.

This. application is a Icontinuation in part, of applicants' copendingapplications 'Serial No. 395,516, filed September 27, 1929, by theapplicants McEachron, Johnson, Jensen and Schroeder, and Serial No.455,226, filed May 24, 1930,

by applicants McEachron and Schroeder.

The cores of this type of cell usually comprise a depolarizing mixtureof manganese dioxide, carbonaceous material, ammonium chloride, zincchloride, and water, prepared as a damp fairly cohering vmass which isgiven form by compression. However, the compressed cores are fragile,and are easily broken or deformed, by ordinary commercial methods ofhandling and disinte:

grate and flake off rapidly when placed into a liquid. Thesecharacteristics present numerous `problems but the use of cores ishighly desirable from a commercial manufacturing stand-v point, and thegeneral practice has therefore been to encase them in what is termed abag, usually consisting of cheese cloth which serves to retain the shapeof the core mass to prevent its disintegration and to prevent the akingoff of particles when it is brought into contact with the ungelatinizedelectrolyte and during the time necessary to convert the electrolytemixture from a milky uid to a relatively sti gelatinous consistency.

The maintenance of the physical form of the core and the prevention ofdisintegration after the core has been placed in the zinc cup, isessential to the production of a satisfactory commercial cell, asthe'scaling off of any particles 0 of depolarizing material and thecollection thereof adjacent the bottom of the cell between the core andthe zinc cup, will cause short circuits in the cell or establish localaction therein which I will entirely destroy the usefulness of the cellas a commercial product, or so materially shorten (Cl. 13G-123) itslife, that it will fall below the standards now demanded for dry cellsin use.

The bag or casing which has heretofore been employed in dry cells,presents certain limitations which cannot be avoided and which are basedupon the following considerations:

In dry cells of the bag type, the core of depolarizing mixture is madeas above described of less diameter than the zinc can and the spacebetween the core and the can is occupied by an electrolyte mixture whichis rendered nonilowable by the gelatinizing action of some suitableagent, such as starch, cereal or similar material. This is necessary inthe type of cell referred to in order to eliminate the -presenceof aflowable' liquid which would leak out of the cell and cause the rapiddisintegration ,of the core of depolarizing mixture in Contact with theungelatinized electrolyte mixture.

The disintegrating action of liquid may be illustrated by placing acompressed core of the type used in the cells here referred to, in acontainer of water, Where it will be noted the core willrapidly'disintegrateand crumble to a powdered mass in the bottom of thecontainer in less than sixty seconds. The necessity for the bag orcasing is therefore apparent and as above mentioned, cheese cloth hasbeen the only material which has been succesesfully used in commercialpractice prior to this invention.

Cheese cloth has heretofore been considered necesary because of itsabsorption and porosity, whereby cheese cloth offers little or noresistance to the passage of the ungelatinized mixture and further itsuse largely avoids the formation of insulating pockets of air filmsbetween the core and the bag. The efficiency of a dry cell of this typedepends upon the maintenance of its composing elements in properintimate association whereby the electric functions may result Withouthindrance, and also the avoidance of air films, bubbles, voids of anykind, evaporation of water, displacement of the core material or anyother condition which will alterthe proper atrangement or association ofthe composing elements.

It is not only essential to establish this degree of perfection for alimited period of time but for increased life of cells and batteries, itis desirable to maintain this perfection to a high degree throughoutsubstantially the entire'electrolytic life of the cell.

Whereas cheese cloth serves well as a casing for the depolarizing core,efforts have been made to find a cheaper substitute material, becausethe relatively high cost of cheese cloth adds materially to the expenseof the cell and batteries, both as a raw material and in labor costs,due to the relatively slow and diflicult manipulation required to applythe cheese cloth casing to the core.

All efforts thus far, however, have failed to produce a satisfactorysubstitute with the result that allcommercial batteries of the bag typewith wrapped cores manufactured at the present time, employ cheese clothcasings for the core notwithstanding the fact that it is extremelyexpensive, and that its installation is slow, tedious and costly. V

' Prior efforts to use paper as a substitute, have provenunsatisfactory, as it was found that the proper degree of porosity couldnot be obtained in a commercially satisfactory manner and further, thatpaper casings or bags formed in effect,

a barrier between the core and the gelatinized electrolyte whichprevented the electrolyte from coming into proper intimate contact withthe depolarizing mixture.

Various efforts have been made to eliminate this difficulty, butadditional difficulties have been encountered. Heretofore, it has beenfound impracticable to commercially produce cells employing paper bagshaving an electric efficiency and life equal to cells employing1 cheesecloth. This was usually due to the existence of an air film between thebag casing and the depolarizing core, which is created either initiallyat the time the cell is assembled during manufacture or later, due tothe entrapping of air, the evaporation of moisture from the spacebetween the core and the bag, or, to other causes. This vdifculty willbe better understood by the following description of the customarymethods now employed for manufacturing cells of this type.

The prevailing manufacturing practice, is substantially as follows:

Zinc cans, carbon pencils and the depolarizing mix are first provided.Thereafter, by suitable machinery, a predetermined quantity,y ofdepolarizing mix is compressed around the carbon pencil to form the coreof any desired siz'e and shape with one end of thecarbon pencilprotruding a slight distance from the end of the core.

The compressing operation serves to mold the depolarizing mix so that itclings together around the imbedded carbon pencil and holds its shape byits natural coherence. Preferably before the cores are compressed, ametal cap is pressed by suitable mechanism, onto `the protruding end ofthe carbon pencil. Then insulating discs are placed in the bottom of thezinc cups. These are preferably made of relatively heavy waxed paper.

lAt this stage, the cores must be handled carefully, because as abovementioned, they are fragile and easily broken or deformed and willdisintegrate and flake off rapidly when in contact with a liquid for aperiod of thirty seconds or more. It next becomes necessary to place thecores so made in the zinc cups, containing an amount of electrolytesufficient to occupy the annular space between the core and the cup, itbeing understood that the core is of slightly less diameter than thecup. Thecups are usually placed in trays, a 'number in one tray,`and ineach is placed the predeterminedl amount of the electrolyte lwhich isusually a solution of Zinc chloride and sal ammoniac. The electrolytealso includes a suitable gelatinizing agent, prefer ably starch, so thatupon the application of suf.-

thus made are thereafter grouped together in cient heat, the liquid willbe gelatinized in a relatively short period after the core has beenplaced in the cup, in contact with the liquid.

In order to avoid the liability of the core scaling off and particlesthereof from coming in contact with the cup, such as might short circuitor otherwise damage the cell, as above described, a core wrapping isprovided.

Inasmuch as cheese cloth is very expensive and involves a difficult andslow manipulation for` its application to the core, this invention isdirected to a substitute core wrapping which will replace cheese clothand yet give corresponding results in electrolytic action whilepermitting a much simpler and cheaperl operation for applying thewrappings to the cores in manufacture.

It is usual in commercial practice, to place small discs of insulatingmaterial in the bottom of the' cups and to thereafter introduce theelectrolyte. Thereafter, cores are placed in the cups mounted in thetrays and a frame having holes therein for receiving the protrudingcarbon pencils is placed over the cells to center the cores within thecups. Upon the introduction of the cores in the cups, the electrolyte isdisplaced and is caused to rise and fill the annular space between thecore and the walls of the cups to the desired level.

Immediately after placing the cores in the cups, that is to say; withinthe period of a few seconds, the tray of cups is placed in a bath of hotwater of sufficient temperature to gelatinize the starch material. Thisoccurs almost at once, at least in a period of time, after the coreshave been introduced, insufficient to permit any substantialdeterioration of the cores by the liquid in contact with them. After theelectrolyte is thoroughly gelatinized, the danger period has passed andthe individual cells are then sealed at the top with a suitable sealingmaterial. The seal is preferably brought to the top of the zinc cup andis designed. to leave the end of the carbon pencil, protruding slightlyto enable a satisfactory electric connection to be made thereto. Thecells suitable retaining cartons or the like, connected and made up intofinished batteries.

The difficulty heretofore encountered in endeavoring to use cheapersubstitute materials for cheesev cloth is attributable to the fact thatno other material has been found which would enable the electrolyte topass through the core wrapper in a manner required to completely expel,in the limited period of a few seconds, the air film which existsbetween the core and the wrapping and to expel all air bubbles whichtend to cling to the wrapping itself before they become frozen in thegelatinized electrolyte.

Failure to eliminate the air in this manner results in a cell which isimperfect from the standpoint of electrical performance. In otherinstances, only a small quantity of electrolyte penetrates the wrappingwhich, after a period, evaporates leaving an undesirable air space asbefore.

More -specifically therefore, the present invention relates to a new andimproved type ,of core wrapping of paper, which is cheap and is of suchkind and is made of such form and shape in its application to the core,that it serves equally as 145 ywell as cheese cloth injthe performanceof the cell v'and yet is --one whichy enables its application by Y'mediately surrounding the core. i tom is'open, the electrolyte with theproper proeral important discoveries which are as follows:

First, that satisfactory cells having paper core wrappings may beprovided when the core wrapping is omitted from the top of the core sothat the upperedge of the wrapping terminates adjacent the upperedge ofthe core so asto leave an opening at the top of the space or crackbetween the core and the wrapping, and provided the paper employed is ofsuch porosity and absorption as topermit the electrolyte solution topass therethrough.` v It is preferable that the paper be of such fibercomposition-.as-to show minute holes therethrough when held up to astrong light. It has been discovered that the elimination of the airfilm between the core and the wrapping is greatly assisted by leavingthe top of the core uncovered in this manner.

Whereas, this feature makes for considerable improvement over all priorefforts to use paper wrappings, and standing alone, constitutes a partof this invention, the vcharacter of the cell may be further improved byadopting in addition to the open top, either one cr both of theadditional improvements hereinafter described.

Secondly, it has been found that additional advantages are realized ifthe Wrapping does not extend completely over the bottom of the core, aswith this arrangement, the electrolyte is free to enter the spacebetween the core and the wrapping from the bottom and rise therein asthe core is inserted downwardly'in the cup, so as to quickly andcompletely expel the air which escapes freely through the top opening.

Whereas, the top opening alone assists greatly in eliminating the airfilm, it is found that substantially all of th'e starch will be filteredout of the electrolyte as it passes through the paper wrapping so thatthe electrolyte which occupies the inner space will not be gelatinizedand will therefore remain as a liquid for long periods with theliability of becoming vaporized in time, creating an air or other space,forming insulation im- Whenthe botportion of starch is permitted tofreely pass into the space between the core and the wrapping whereby theelectrolyte inside the Wrapping is gelatinized the same as on theoutside.

In this form, the wrapping may terminate flush with the bottom edge ofthe core and the insulating disk will serve to prevent sh'ort circuitsor local action by any particles or crumbs which may drop to the bottomin the space between the core and wrapping. However, as a precaution it'is desirable to provide the Wrapping of a length greater than theheight of the core so that the lower margin thereof may be folded ashort distance at the lower edge of the core to under-lie the rimportion of the core base.

Wrappings of this type are foundgto provide sufficient opening andclearance for the `free passage of the starch and electrolyte into thespace between the core and the wrappings.

Thirdly, in addition to the above discoveries, it has"been also foundthat if paper of the above described type is provided with a pluralityof perforations therethrough of approximately, say

faf to -ll of Jan inch in diameter and from approximately 1/4 to 1/2 ofan inch apart, extending in both directions, the free passage of theelectrolyte and starch into the space between the core and the wrappingis materially assisted without in any way detracting from theeffectiveness of the wrapper. Wrappers so provided are productive ofcells which are in every respect, equal to the cells having cheese clothwrappers, yet they may be produced at a great reduction in cost both asto material and in manufacture.

In order to more clearly illustrate this invention, reference will nowbe made to the accompanying drawing, in which- Figure 1 is anelevational view in cross section of a cell embodying one form of thepresent invention and Figure 2 is a perspective view vof the core andwrapper construction shown in Figure- 1;

Figure 3 is a view showing the wrapper before it is applied t'o thecore.

Figure 4 is a perspective view of a modied form of core andwrapperconstructed in accordance with this invention and Figure 5 isasimilar view of another modified form of core and wrapper construction.

Figure 6 is a view similar to Figure l, showing a cell having arectangular can and core, also embodying features of this invention andFiguresy 7 and 8 are perspective `views showing the rectangular core ofFigure 6 and the manner of applying the core wrapper thereto.

By referring to the drawing, it will be noted that one form ofthisinvention is illustrated as embodied in a cell shown in Figure 1,comprising a zinc cup 10, having an insulating disk 11 placed in thebottom thereof-with a suitable quantity of electrolyte 12, forsurrounding the core. The construction of the core here used is clearlyshown in Figures 1 and 2 and comprises the car,- bon pencil 13 havingthe metallic cap 14 on -the upper end thereof and the mass 15, ofdepolarizing mixture.

Surrounding the sides of the core, is a paper wrapper 16, which isformed of such length that the upper edgethereof may terminatesubstantially iiush with the upper edge of the core or slightly above,as shown in Figure 1 and the lower edge folded under the base of thecore as at 17, shown in Figures l and 2. The wrapper preferably overlapsa short distance along its vertical edge and is held in place by a gluedstrip or sticker 18.

The wrapper is composed of a paper which is permeable enough to allowthe electrolyte to pass therethrough in order to expel the lm of airdisposed between theA wrapper and the core.`

This space is shown in Figure 1 and is designated film of air issuflicient to impair the electrolytic 1.

action of the cell unless `it is completely expelled during the cellforming operation.

The exaggerated showing in the drawing is given in order to more clearlyillustrate the problems herein `referred to and the nature of thepresent invention in solving same.

An important feature of this construction is that the top of the core isleft uncovered so that the space 20 is vented at the top whereby theelectrolyte in passing into this space can displace the air upwardly andthereby efficiently eliminate the undesirable air lm referred to. 'Anadditional feature of this constructionis thetype of paper employed.There are several kindsof paper which may be used, preferably avegetable fiber, but it must possess the characteristics of being porousand penneable. Examples of satisfactory paper are, paper towelllng,battery board, including sulphate pulp and ground wood, and even-cheap,sized writing paper Gli not suitable for writing in ink. One of the best-examples of satisfactory paper for the present wrapper consists of 100per cent pulp containing no filler or sizing which has not beencalendered and is preferably creped. As above mentioned, the fiberconstruchon of this paper should be such that minute openings may bedetected in the pores thereof when placed in front of a strong light.

v Additional features of the construction of this invention are theholes 21, provided in the wrapper in such size and number that theelectrolyte with its gelatinizing starch can freely pass into the space20. The openings are preferably between one thirty-second and onesixteenth of an inch in diameter and may be placed between one quarterand one half of an inch apart in both directions.

Further, the bottom of the core is left substantially uncovered so thatthe electrolyte with the gelatinizing starch is free to enter the space20 from the bottom as the core is inserted into the cup. The overlap 17,at the bottom, has substantially no retarding effect upon the passage ofthe liquid and starch into the space and yet it serves as a verysatisfactory protection in conjunction With the insulating disk 1l, ofwaxed or greased paper to prevent any-possibility of short clrcuiting orlocal action by particles which may fall from the sides of the coredownwardly in the space 20. After the core is lplaced in the cup aninsulating disk 22 having a central opening'23is positioned around thepencil and in engagement with the cup in the manner shown in Figure lwhereby it acts as a centering device for the core as Well as a supportfor the sealing material 24, placed on the top thereof. The seal 24, maybe of wax or a similar material now commercially used in this art and isso applied that the metallic cap on the upper end of the carbon pencilis left exposed to an extent sufiicient to make a satisfactoryelectrical connection thereto.

As an alternative crm of the present invention, the core may be made asshown in Figure 5, in which case the wrapper terminates ilush with thelower edge of the core and is not provided with the under-lying fold1'7, as shown in Figure l. Furthermore, the paper maybe made without theperforations 21 in the sides thereofleaving only the bottom and topopenings together with the pores in the paper for .effecting thedisplacement of the air film. The form with the holes omitted is not asdesirable as that shown in Figure 1, but notwithstanding, it constitutesa decided improvement over the prior art which renders it possible touse paper wrappings instead of cheese cloth.

Accordingly, this invention should be con strued sufficiently broad tocover this type of cell. In any of the forms, here illustrated, themanner of securing the wrapper may be varied according to particularcircumstances, whereby if it is desired, a rubber band 25, shownT inFigure 4, may be used, instead of the paper sticker 18, shown in Figure2.

In practice, the rubber band is found to exert suicient constrictingforce upon the wrapper to hold it tightly in place and yet havesubstantially no retarding eiect on the displacement of air in the space20.

A further form of the invention is shown in Figures 6 to 8 inclusive, inwhich a rectangular core is provided, and in connection with which, isalso illustrated that embodiment of thepresent invention wherein thewrapper is folded over the lower edge of the core to cover the entirebottom thereof.

As Figure 6 is the same in all essential principles as the showing inFigure 1, corresponding parts thereof will be designated by likereference numerals where this is practical.

The core shown in Figures 7 and 8 will be made in substantially the sameway as the cylindrical core except that the core forming press will besuitably modified. The wrapper here shown in addition to being foldedover the bottom of the core may be made with or without perforations inthe sides thereof as shown in Figures 1 and 2.

Furthermore, the wrapper may be held in place by the rubber band 25, asshown, or if desired, by means of a sticker, as shown at 18, in Figure2.

In commercial manufacture it is desirable in certain instances, toprovide cores of rectangular shape. In such cases, improved results arerealized by wrapping the core at the bottom in the manner shown inFigures '7 and 8. The wrappers may be either without perforations asshown in said figures, or preferably with perforations as shown inFigure 3. As a manufacturing proposition, it is less difcult to providethe folded bottom as shown in Figure 8, with rectangular cores than itis to provide the tucked-under bottom of thetype shown on the round corein Figure 2. With the type of porous paper above specified, and the opentop, this form of wrapping is found to serve well.

It should be understood that any combination of the features hereindescribed as important are contemplated for this invention and that incertain instances,l all or various combinations thereof may be embodiedin a cell of commercial construction or on the other hand, certain onesalone may be utilized according to the dictates of manufacture and thetype of cell desired.

We claim:

1. An electrical cell of the bag type, comprising a zinc cup, a wrappedcore of compressed depolarizing mixture and an embedded carbon pencil,in said cup with a space, between said wrapped core and the sides ofsaid cup, a gelatinized electrolyte in said space, and an insulatingmaterial between the bottom of said core and cup, the wrapper for saidcore being of porous, absorbent paper covering the sides of said corewhile leaving the top thereof uncovered whereby to provide a free andunobstructed vent at the top of said core for the escape of airordinarily confined between said core and wrapper.

2. An electrical cell of the lbag type, comprising a zinc cup, a wrappedcore of compressed depolarized mixture and an embedded carbon pencil, insaid cup with a space between said wrapped core and the sides of saidcup, a gelatinized electrolyte in said space, and an insulating materialbetween the bottom of said core and cup, the wrapper for said core beingof porous, absorbent paper covering the sides of said core while leavingthe top thereof uncovered whereby to provide a free and unobstructedvent at the top of said core for the escape of air ordinarily confinedbetween said core and Wrapper, said wrapper having a pluralityv ofminute holes therethrough, distributed over its area to overlie at leasta portion of the sides of said core, said holes being of such size as topermit the free passage of gelatinizable electrolyte while confining anyfree particles which may become loosened from said core.

3. An electrical cell of the bag type, comprising a zinc cup, a Wrappedcore of compressed depolarizing mixture and an embedded carbon pencil,lin` said cup with a space between said wrapped core and the sides ofsaid cup, a gelatinized electrolyte in said space, and an insulatingmaterial between the bottom of said core and cup, the wrapper for saidcore being of porous, absorbent papercovering the sides and marginalarea of the bottom of said' core while leaving the top and the centralbottom portions thereof uncovered whereby to provide a free andunobstructed vent at the top of said core and a free passage forgelatinizable electrolyte at the bottom of said core, for the readydisplacement and escape of air ordinarily Aconfined between said coreand wrapper.

4. An electrical cell of the bag type, comprising a zinc cup, a wrappedcore of compressed depolarizing mixture andan embedded carbon pencil, insaid cup with a space between said wrapped core and the sides of saidcup, a gelatinized electrolyte in said space, and an insulating materialbetween the bottom of said core and cup, the wrapper for said core beingof porous, absorbent paper covering the sides and marginal area of thebottom of said core while leaving the top and the central bottomportions thereof uncovered, whereby to provide a free and unobH structedvent at'the top of said core and a free,

passage iorgelatinizable electrolyte at the bottom of said core, for theready displacement and escape of air ordinarily conned between said coreand wrapper, said wrapper having a plurality ofv minute holestherethrough, distributed over its area to overlie at least a portion ofthe sides oi.' said core, said holes being of such size as to permit thefree passage of gelatinizable electrolyte while coniining any freeparticles which may become loosened from said core.

5. An electrical cell of the bag type, comprising a zinc cup, a wrappedcore of compressed depolarizing mixture and an embedded carbon pencil,in said cup with a space between said wrapped core and the sides of saidcup, a gelatinized electrolyte in said space, and an insulating materialbetween the bottom of said core and cup, the wrapper for said core beingof porous, absorbent paper covering the sides of said core while leavingthe top thereof uncovered whereby to provide a free and unobstructedvent at the top of said core for the escape of air ordinarily confinedbetween said core and wrapper, said wrapper extending verticallyupwardly along the sides of said core with its upper edge disposedslightly above the upper edge of saidcore.

EDGAR J. MCEAC'HRON. REGINALD S. JOHNSON. HAROLD G. JENSEN. O'I'IO E.RUHOFF. GEORGE SCHROEDER. OTTO J, KRUEGER.

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